BIOLOGY 3P03 Lecture Notes - Lecture 21: Cyclic Adenosine Monophosphate, Metastasis, Keratin
28 Dec 2017
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Document Summary
The evolution of higher organisms required that single cells rst formed multicellular associations. One multicellularity evolved, this allowed individual cells or groups of cells to specialize for speci c functions. It likely all began with the rst cell adhesion molecules. Adhesive molecules allow cells to maintain contact with one another and with structures in the extracellular matrix. Epithelial tissues form barriers between body compartments and surface layers facing the environment. Tissues made up of epithelia include : skin, kidney, gall bladder, urinary bladder, intestine, salivary and lacrimal glands, sweat glands, trachea, and sh gills. Functions carried out by epithelia include : osmoregulation, ionoregulation, exocrine gland secretion, digestion, absorption, and acid-based balance. Adhering junctions/zonula adherens- composed of actin laments and cadherins- Desmosomes/macula adherens- composed of intermediate laments, cadherins, and plaque- form circular connections. Gap junctions- composed of connexons- aid in signalling between cells.
